DE102018109725A1 - PASSIVE NOx ADSORBER - Google Patents

Abstract

Described is a NO _x absorber catalyst for treating an exhaust gas from a diesel engine. The NO _x absorber catalyst comprises a first region comprising a NO _x absorbent material comprising a molecular sieve catalyst and a second region comprising a nitrogen dioxide reduction material and a substrate having an inlet end and an outlet end.

Description

FIELD OF THE INVENTION

The present invention relates to a lean burn NO _x absorbent catalyst and an lean burn engine exhaust system comprising the NO _x absorber catalyst. The invention further relates to a method of using the NO _x absorber catalyst to treat an exhaust gas from a lean burn engine.

BACKGROUND OF THE INVENTION

Lean-burn engines, such as diesel engines, produce an exhaust emission that generally contains at least four classes of pollutants that have been legislated by international organizations around the world: carbon monoxide (CO), unburned hydrocarbons (HCs), nitrogen oxides (NO _X ), and particulate matter Material or fine dust (PM).

There are a variety of emission control devices for the treatment of nitrogen oxides (NO _x ). These devices comprise for example a selective catalytic reduction (SCR) catalyst, a selective catalytic reduction filter (SCRF ™) catalyst, a lean _NOx catalyst [for example, a hydrocarbon (HC) SCR catalyst], a lean -NO _X trap (LNT) [also known as NO _x storage catalyst (NSC) or NO _x adsorber catalyst (NAC)] and a passive NO _x adsorber (PNA).

SCR catalysts or SCRF ™ catalysts typically achieve high efficiencies for the treatment of NO _X by reduction once they have reached their effective operating temperature. However, these catalysts or devices may be relatively inefficient below their effective operating temperature, for example, when the engine has been started from a cold state ("cold start" period) or has been idle for an extended period of time.

Another common type of emission control apparatus for reducing or preventing the emission of NO _X is a lean _NOx trap (LNT). During normal operation, a lean burn engine produces exhaust emission with a "lean" composition. An LNT is capable of storing or trapping the nitrogen oxides (NO _x ) present in the "lean" exhaust emission. The LNT stores or captures the in the exhaust emission existing NO _X by a chemical reaction between the NO _x and a NO _x storage component of the LNT to form an inorganic nitrate, a. The amount of NO _X that can be stored by the LNT is limited by the amount of NO _X storage component present. Finally, it is necessary to release the stored NO _X from the NO _X storage component of the LNT, ideally when a downstream SCR or SCRF ™ catalyst has reached its effective operating temperature. The release of stored NO _X from an LNT is typically by running the engine lean mixture for producing an exhaust emission having a composition "fat" achieved under rich conditions. Under these conditions, the inorganic nitrates of the NO _x storage component decompose to form NO _{x again} . This requirement for flushing an LNT under rich conditions is a disadvantage of this type of emission control device, as it compromises the fuel economy of the vehicle and increases the amount of carbon dioxide (CO ₂ ) by combustion of additional fuel. LNTs also tend to show poor NO _x storage efficiency at low temperatures.

A relatively new type of emission control device for NO _x is a passive NO _x adsorber (PNA). PNAs are able to adsorb or adsorb NO _x at relatively low exhaust gas temperatures (eg, less than 200 ° C), usually by adsorption, and release NO _X at higher temperatures. The NO _X storage and release mechanism of PNAs is thermally controlled, unlike that of LNTs, which require a rich purge to release stored NO _X.

SUMMARY OF THE INVENTION

• eine erste Region, die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, wobei der Molekularsiebkatalysator ein Edelmetall und ein erstes Molekularsieb umfasst, und wobei das erste Molekularsieb das Edelmetall enthält;
• eine zweite Region, die ein Stickstoffdioxid-Reduktionsmaterial umfasst, das mindestens ein anorganisches Oxid umfasst; und
• ein Substrat mit einem Einlassende und einem Auslassende;

wobei die zweite Region im Wesentlichen frei von Platingruppenmetallen ist.In a first aspect of the invention, there is provided a NO _x absorber catalyst for treating an exhaust gas from a diesel engine, comprising:

• a first region comprising a NO _x absorber material comprising a molecular sieve catalyst, wherein the molecular sieve catalyst comprises a noble metal and a first molecular sieve, and wherein the first molecular sieve contains the noble metal;
• a second region comprising a nitrogen dioxide reducing material comprising at least one inorganic oxide; and
• a substrate having an inlet end and an outlet end;

wherein the second region is substantially free of platinum group metals.

In a second aspect, the invention further provides an exhaust system for a lean burn engine, such as a diesel engine. The exhaust system includes a NO _x absorber catalyst of the invention and an emission control device.

In a third aspect, the invention provides a vehicle comprising a lean burn engine and either the NO _x absorber catalyst or the exhaust system of the invention.

In a fourth aspect, the invention provides a method of treating an exhaust gas from a lean burn engine, the method comprising either contacting the exhaust with an NO _x absorber catalyst of the invention or passing the exhaust through an exhaust system of the invention.

list of figures

• 1 zeigt einen NO_X-Absorberkatalysator mit der ersten Region (1), die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, und der zweiten Region (2), die ein Stickstoffdioxid-Reduktionsmaterial umfasst, wobei beide auf einem Substrat (3) angeordnet sind, das ein Einlassende und ein Auslassende aufweist. Die zweite Region (2) befindet sich stromauf (bezüglich einer Gasströmungsrichtung bei Verwendung) der ersten Region (1).
• 2 zeigt einen NO_X-Absorberkatalysator mit einer ersten Region (1), die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, und einer zweiten Region/Zone (2), die ein Stickstoffdioxid-Reduktionsmaterial umfasst. Es gibt eine Überlappung zwischen der ersten Region und der zweiten Region/Zone. Ein Teil der ersten Region ist auf der zweiten Region/Zone angeordnet. Sowohl die erste Region als auch die zweite Region/Zone sind auf dem Substrat (3) angeordnet.
• 3 zeigt einen NO_X-Absorberkatalysator mit einer ersten Region (1), die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, und einer zweiten Region/Zone (2), die ein Stickstoffdioxid-Reduktionsmaterial umfasst. Es gibt eine Überlappung zwischen der ersten Region/Zone und der zweiten Region. Ein Teil der zweiten Region ist auf der ersten Region/Zone angeordnet. Sowohl die erste Region/Zone als auch die zweite Region sind auf dem Substrat (3) angeordnet.
• 4 zeigt einen NO_X-Absorberkatalysator mit einer ersten Schicht (1), die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, die auf einer zweiten Schicht (2), die ein Stickstoffdioxid-Reduktionsmaterial umfasst, angeordnet ist. Die zweite Schicht ist auf dem Substrat (3) angeordnet.
• 5 zeigt einen NO_X-Absorberkatalysator mit einer zweiten Schicht (2), die ein Stickstoffdioxid-Reduktionsmaterial umfasst, die auf einer ersten Schicht (1), die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, angeordnet ist. Die erste Schicht ist auf dem Substrat (3) angeordnet.
• 6 zeigt einen NO_X-Absorberkatalysator mit einer ein Dieseloxidationskatalysatormaterial umfassenden Schicht (4), die auf einer zweiten Region/Schicht (2) angeordnet ist. Die zweite Region/Schicht (2) umfasst das Stickstoffdioxid-Reduktionsmaterial. Die zweite Region/Schicht (2) ist auf der ersten Region/Schicht (1), die einen Molekularsiebkatalysator umfasst, angeordnet. Die erste Region/Schicht (1) ist auf dem Substrat (3) angeordnet.
• 7 zeigt einen NO_X-Absorberkatalysator mit einer ein Dieseloxidationskatalysatormaterial umfassenden Schicht (4), die auf einer ersten Schicht angeordnet ist, wobei die erste Schicht eine erste Region (1) und eine zweite Region (2) umfasst. Die erste Region (1) umfasst ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial. Die zweite Region (2) umfasst ein Stickstoffdioxid-Reduktionsmaterial. Die erste Region (1) ist stromab der zweiten Region (2) angeordnet. Die erste Region (1) und die zweite Region (2) sind beide auf einem Substrat (3) angeordnet.
• 8 zeigt einen NO_X-Absorberkatalysator, der eine Schicht (4), die ein auf einer ersten Schicht angeordnetes Dieseloxidationskatalysatormaterial umfasst, wobei die erste Schicht eine erste Region (1) und eine zweite Region (2) umfasst, aufweist. Die erste Region (1) umfasst ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial. Die zweite Region (2) umfasst ein Stickstoffdioxid-Reduktionsmaterial. Die erste Region (1) ist stromab der zweiten Region (2) angeordnet. Die erste Region (1) und die zweite Region (2) sind beide auf einem Substrat (3) angeordnet.

The 1 to 8th are schematic representations of NO _x absorber catalysts of the invention.

• 1 Figure 12 shows a NO _x absorber catalyst having the first region (1) comprising a NO _x absorbent material comprising a molecular sieve catalyst and the second region (2) comprising a nitrogen dioxide reduction material both disposed on a substrate (3) having an inlet end and an outlet end. The second region (2) is upstream (with respect to a gas flow direction in use) of the first region (1).
• 2 Figure 4 shows a NO _x absorber catalyst having a first region (1) comprising a NO _x absorbent material comprising a molecular sieve catalyst and a second region / zone (2) comprising a nitrogen dioxide reduction material. There is an overlap between the first region and the second region / zone. Part of the first region is located on the second region / zone. Both the first region and the second region / zone are arranged on the substrate (3).
• 3 Figure 4 shows a NO _x absorber catalyst having a first region (1) comprising a NO _x absorbent material comprising a molecular sieve catalyst and a second region / zone (2) comprising a nitrogen dioxide reduction material. There is an overlap between the first region / zone and the second region. Part of the second region is located on the first region / zone. Both the first region / zone and the second region are disposed on the substrate (3).
• 4 Figure 11 shows a NO _x absorber catalyst having a first layer (1) comprising a NO _x absorber material comprising a molecular sieve catalyst disposed on a second layer (2) comprising a nitrogen dioxide reduction material. The second layer is arranged on the substrate (3).
• 5 Figure 4 shows a NO _x absorber catalyst having a second layer (2) comprising a nitrogen dioxide reducing material disposed on a first layer (1) comprising a NO _x absorbent material comprising a molecular sieve catalyst. The first layer is arranged on the substrate (3).
• 6 Figure 4 shows a NO _x absorber catalyst with a layer (4) comprising a diesel oxidation catalyst material disposed on a second region / layer (2). The second region / layer (2) comprises the nitrogen dioxide reducing material. The second region / layer (2) is disposed on the first region / layer (1) comprising a molecular sieve catalyst. The first region / layer (1) is arranged on the substrate (3).
• 7 shows a NO _x absorber catalyst comprising a layer (4) comprising a diesel oxidation catalyst material disposed on a first layer, the first layer comprising a first region (1) and a second region (2). The first region (1) comprises a NO _x absorbent material comprising a molecular sieve catalyst. The second region (2) comprises a nitrogen dioxide reducing material. The first region (1) is located downstream of the second region (2). The first region (1) and the second region (2) are both arranged on a substrate (3).
• 8th Figure 11 shows a NO _x absorber catalyst comprising a layer (4) comprising a diesel oxidation catalyst material disposed on a first layer, the first layer comprising a first region (1) and a second region (2). The first region (1) comprises a NO _x absorbent material comprising a molecular sieve catalyst. The second region (2) comprises a nitrogen dioxide reducing material. The first region (1) is located downstream of the second region (2). The first region (1) and the second region (2) are both arranged on a substrate (3).

DEFINITIONS

The term "region" as used herein refers to a region of a washcoat on a substrate. For example, a "region" may be disposed or supported on a substrate in the form of a "layer" or "zone". The area or arrangement of a washcoat on a substrate is generally controlled during the process of applying the washcoat to the substrate. The "region" typically has distinct boundaries or edges (i.e., it is possible to distinguish one region from another region using conventional analysis techniques).

Typically, the "region" has a substantially uniform length. The reference to a "substantially uniform length" in this context refers to a length which does not deviate from its mean value by more than 10% (eg the difference between the maximum and minimum length), preferably deviates by no more than 5% , more preferably not more than 1%.

It is preferred that each "region" has a substantially uniform composition (i.e., there is no significant difference in the composition of the washcoat when comparing one part of the region to another part of that region). A substantially uniform composition in this context refers to a material (eg, region) in which the difference in composition when comparing part of the region to another part of the region is 5% or less, usually 2.5% or less, and most commonly 1% or less.

The term "zone" as used herein refers to a region having a length less than the total length of the substrate, e.g. ≤ 75% of the total length of the substrate. A "zone" typically has a length (i.e., a substantially uniform length) of at least 5% (e.g., ≥ 5%) of the total length of the substrate.

The total length of a substrate is the distance between its inlet end and its outlet end (e.g., the opposite ends of the substrate).

Any reference herein to a "zone disposed at an inlet end of the substrate" refers to a zone disposed or supported on a substrate, which zone is closer to an inlet end of the substrate than the zone is to an outlet end of the substrate. Thus, the midpoint of the zone (i.e., at half its length) is closer to the inlet end of the substrate than the midpoint is to the outlet end of the substrate. Similarly, any reference herein to a "zone disposed at an outlet end of the substrate" refers to a zone disposed or supported on a substrate, the zone being closer to an outlet end of the substrate than the zone is to an inlet end of the substrate. Thus, the midpoint of the zone (i.e., at half its length) is closer to the outlet end of the substrate than the midpoint is to the inlet end of the substrate.

1. (a) sich näher zu einem Einlassende (z.B. einem offenen Ende) eines Einlasskanals des Substrats befindet als sich die Zone sich zu einem verschlossenen Ende (z.B. einem blockierten oder verstopften Ende) des Einlasskanals befindet, und/oder
2. (b) sich näher zu einem verschlossenen Ende (z.B. einem blockierten oder verstopften Ende) eines Auslasskanals des Substrats befindet als sich die Zone zu einem Auslassende (z.B. einem offenen Ende) des Auslasskanals befindet.

In general, when the substrate is a wall-flow filter, any reference to a "zone disposed at an inlet end of the substrate" refers to a zone disposed or supported on the substrate that:

1. (a) is closer to an inlet end (eg, an open end) of an inlet channel of the substrate than the zone is to a closed end (eg, a blocked or plugged end) of the inlet channel, and / or
2. (b) is closer to a closed end (eg, a blocked or plugged end) of an outlet channel of the substrate than the zone is to an outlet end (eg, an open end) of the outlet channel.

Thus, the midpoint of the zone (ie, at half its length) is (a) closer to an inlet end of an inlet channel of the substrate than the midpoint to the closed end of the inlet channel, and / or (b) closer to an occluded end of a Outlet channel of the substrate as the center is located to an outlet end of the outlet channel.

1. (a) sich näher zu einem Auslassende (z.B. einem offenen Ende) eines Auslasskanals des Substrats befindet als sich die Zone zu einem verschlossenen Ende (z.B. einem blockierten oder verstopften Ende) des Auslasskanals befindet, und/oder
2. (b) sich näher zu einem verschlossenen Ende (z.B. einem blockierten oder verstopften Ende) eines Einlasskanals des Substrats befindet als sie sich zu einem Einlassende (z.B. einem offenen Ende) des Einlasskanals befindet.

Similarly, when the substrate is a wall-flow filter, any reference to a "zone disposed at an outlet end of the substrate" means a zone disposed or supported on the substrate that:

1. (a) is closer to an outlet end (eg, an open end) of an outlet channel of the substrate than the zone is to a closed end (eg, a blocked or plugged end) of the outlet channel, and / or
2. (b) is closer to a closed end (eg, a blocked or plugged end) of an inlet channel of the substrate than it is to an inlet end (eg, an open end) of the inlet channel.

Thus, the mid-point of the zone (ie, at half its length) is (a) closer to an outlet end of an exhaust passage of the substrate than the midpoint to the closed end of the exhaust passage, and / or (b) closer to a closed end of an intake passage of the substrate as being the midpoint to an inlet end of the inlet channel.

A zone may satisfy both (a) and (b) if the washcoat is present in the wall of the wall-flow filter (i.e., the zone is in the wall or in the walls).

The term "washcoat" is well known in the art and refers to an adherent coating that is typically applied to a substrate during the production of a catalyst.

The term "noble metal" as used herein generally refers to a metal selected from the group consisting of ruthenium, rhodium, palladium, silver, osmium, iridium, platinum and gold. In general, the term "noble metal" preferably refers to a metal selected from the group consisting of rhodium, platinum, palladium and gold.

The acronym "PGM" as used herein refers to "platinum group metal". The term "platinum group metal" generally refers to a metal selected from the group consisting of Ru, Rh, Pd, Os, Ir and Pt, preferably a metal selected from the group consisting of Ru, Rh, Pd, Ir and Pt. In general, the term "PGM" preferably refers to a metal selected from the group consisting of Rh, Pt and Pd.

The term "adsorbent" as used herein, especially in the context of a NO _x adsorber, should not be construed as being limited to the storage or trapping of a chemical entity (eg, NO _X ) merely by adsorption. The term "adsorber" used here is synonymous with "absorber".

The term "mixed oxide" as used herein refers generally to a mixture of oxides in a single phase, as is conventionally known in the art. The term "composite oxide" as used herein refers generally to a composition of oxides having more than one phase, as is conventionally known in the art.

The term "consisting essentially of" as used herein limits the scope of a feature to include the specified materials, as well as any other materials or steps that do not materially affect the basic characteristics of this feature, such as minor contaminants. The term "consists essentially of" includes the term "consisting of".

The term "substantially free of" as used herein with reference to a material, typically in the context of the content of a region, layer or zone, means that the material is added in a low addition amount, such as ≤ 5 wt %, preferably ≦ 2% by weight, more preferably ≦ 1% by weight. The term "substantially free of" includes the term "does not include".

Any reference to an amount of a dopant, in particular a total amount, as used herein, as% by weight, or expressed as weight percent, refers to the weight of the carrier material or refractory metal oxide thereof.

The term "substantially free of" as used herein with reference to a material means that the material is in a low added amount, such as ≤5 wt%, preferably ≤2 wt%, more preferably ≤1 Wt .-%, may be present. The term "substantially free of" includes the term "does not include".

The term "loading" as used herein refers to a measurement in units of g / ft ³ on a metal weight basis.

DETAILED DESCRIPTION OF THE INVENTION

• eine erste Region, die ein einen Molekularsiebkatalysator umfassendes NO_X-Absorbermaterial umfasst, wobei der Molekularsiebkatalysator ein Edelmetall und ein erstes Molekularsieb umfasst, und wobei das erste Molekularsieb das Edelmetall enthält;
• eine zweite Region, die ein Stickstoffdioxid-Reduktionsmaterial umfasst, das mindestens ein anorganisches Oxid umfasst; und
• ein Substrat mit einem Einlassende und einem Auslassende;

wobei die zweite Region im Wesentlichen frei von Platingruppenmetallen ist.The NO _x absorber catalyst of the invention is intended for use as a passive NO _x absorber (PNA). The NO _x absorber catalyst comprises or may consist essentially of a NO _x absorber catalyst for treating an exhaust gas from a diesel engine, comprising:

• a first region comprising a NO _x absorber material comprising a molecular sieve catalyst, wherein the molecular sieve catalyst comprises a noble metal and a first molecular sieve, and wherein the first molecular sieve contains the noble metal;
• a second region comprising a nitrogen dioxide reducing material comprising at least one inorganic oxide; and
• a substrate having an inlet end and an outlet end;

wherein the second region is substantially free of platinum group metals.

In general, the NO _x absorbent material is a passive NO _x absorber (PNA) catalyst (ie, it has PNA activity).

The first region comprises or may consist essentially of a NO _x absorber material. The NO _x absorbent material comprises or consists essentially of a molecular sieve catalyst. The molecular sieve catalyst comprises, consists essentially of or consists of a noble metal and a molecular sieve. The molecular sieve contains the precious metal. The molecular sieve catalyst can according to the in the WO 2012/166868 be prepared described methods.

The noble metal is typically selected from the group consisting of palladium (Pd), platinum (Pt), rhodium (Rh), gold (Au), silver (Ag), iridium (Ir), ruthenium (Ru) and mixtures of two or more more of this exists. Preferably, the noble metal is selected from the group consisting of palladium (Pd), platinum (Pt) and rhodium (Rh). More preferably, the noble metal is selected from palladium (Pd), platinum (Pt) and a mixture thereof. Particularly preferred is the noble metal palladium (Pd).

Generally, it is preferred that the noble metal be palladium (Pd) and optionally a second metal selected from among platinum (Pt), rhodium (Rh), gold (Au), silver (Ag), iridium (Ir) and ruthenium (Ru ) existing group comprises, comprises or consists of. Preferably, the noble metal comprises palladium (Pd) and optionally a second metal selected from the group consisting of platinum (Pt) and rhodium (Rh), or consists thereof. More preferably, the noble metal comprises or consists of palladium (Pd) and optionally platinum (Pt). More preferably, the molecular sieve catalyst comprises palladium as the sole noble metal.

When the noble metal comprises or consists of palladium (Pd) and a second metal, the mass ratio of palladium (Pd) to the second metal is> 1: 1. More preferably, the mass ratio of palladium (Pd) to the second metal is> 1: 1, and the molar ratio of palladium (Pd) to the second metal is> 1: 1.

The molecular sieve catalyst may further comprise a non-noble metal. Thus, the molecular sieve catalyst may comprise or consist essentially of a noble metal, a first molecular sieve, and optionally a non-noble metal. The first molecular sieve contains the precious metal and optionally the base metal.

The base metal may be selected from the group consisting of iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni), zinc (Zn) and tin (Sn ) as well as mixtures of two or more consists thereof. It is preferable that the base metal is selected from the group consisting of iron, copper and cobalt, more preferably iron and copper. Even more preferred is the base metal iron.

Alternatively, the molecular sieve catalyst may be substantially free of a base metal such as a base metal selected from iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni). , Zinc (Zn) and tin (Sn), and mixtures of two or more thereof. Thus, the molecular sieve catalyst can not comprise a base metal.

In general, it is preferred that the molecular sieve catalyst does not comprise a base metal.

It may be preferred that the molecular sieve catalyst is substantially free of barium (Ba), more preferably the molecular sieve catalyst is substantially free of an alkaline earth metal. Thus, the molecular sieve catalyst may not comprise barium, and preferably the molecular sieve catalyst does not comprise an alkaline earth metal.

The first molecular sieve is typically composed of aluminum, silicon and / or phosphorus. The molecular sieve generally has a three-dimensional arrangement (eg a framework) of SiO ₄ , AlO ₄ and / or PO ₄ , which are interconnected by common oxygen atoms. The molecular sieve may have an anionic skeleton. The charge of the anionic skeleton may be balanced by cations, such as by cations of the alkali and / or alkaline earth elements (eg Na, K, Mg, Ca, Sr and Ba), ammonium cations and / or protons.

Typically, the first molecular sieve comprises an aluminosilicate skeleton, an aluminophosphate skeleton or a silicoaluminophosphate skeleton. The first molecular sieve may comprise an aluminosilicate skeleton or an aluminophosphate skeleton. It is preferable that the first molecular sieve has an aluminosilicate skeleton or a silicoaluminophosphate skeleton. More preferably, the first molecular sieve has an aluminosilicate skeleton.

When the first molecular sieve comprises an aluminosilicate skeleton, the molecular sieve is preferably a zeolite.

The first molecular sieve contains the precious metal. The noble metal is typically supported on the first molecular sieve. For example, the noble metal can be loaded onto the molecular sieve and supported on the first molecular sieve, for example by ion exchange. Thus, the molecular sieve catalyst may comprise or consist essentially of a noble metal and a first molecular sieve, wherein the first molecular sieve contains the noble metal, and wherein the noble metal is charged to the first molecular sieve by ion exchange and / or carried on the first molecular sieve.

In general, the first molecular sieve may be a metal-substituted molecular sieve (e.g., a metal-substituted molecular sieve having an aluminosilicate or an aluminophosphate backbone). The metal of the metal-substituted molecular sieve may be the noble metal (e.g., the molecular sieve is a noble metal-substituted molecular sieve). Thus, the noble metal-containing first molecular sieve may be a noble metal-substituted molecular sieve. When the molecular sieve catalyst comprises a non-noble metal, the first molecular sieve may be a noble metal and a base metal substituted molecular sieve. To avoid misunderstanding, it should be noted that the term "metal-substituted" or "substituted with a metal" includes the term "ion-exchanged".

Generally, at least 1 wt% (ie, the amount of the noble metal of the molecular sieve catalyst), preferably at least 5 wt%, more preferably at least 10 wt%, such as at least 25 wt%, is more preferably present in the molecular sieve catalyst preferably at least 50% by weight of the noble metal inside the pores of the first molecular sieve.

The first molecular sieve may consist of a small pore molecular sieve (ie, a molecular sieve having a maximum ring size of eight tetrahedral atoms), a medium pore molecular sieve (ie, a molecular sieve having a maximum ring size of ten tetrahedral atoms) and a large pore molecular sieve (ie, a molecular sieve having a maximum ring size of twelve tetrahedral atoms). More preferably, the first molecular sieve is selected from a small pore molecular sieve and a medium pore molecular sieve.

In a first molecular sieve catalyst embodiment, the first molecular sieve is a small pore molecular sieve. The small-pore molecular sieve preferably has a framework type selected from the group selected from ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW , LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, STI, THO, TSC, UEI, UFI, VNI, YUG and ZON, and any mixture or intergrowth of any two or more of them. The adhesion is preferably selected from KFI-SIV, ITE-RTH, AEW-UEI, AEI-CHA and AEI-SAV. More preferably, the small pore molecular sieve has a framework type which is STI, AEI, CHA or AEI-CHA intergrowth. Even more preferably, the small pore molecular sieve has a framework type which is AEI or CHA, especially AEI.

The small-pore molecular sieve preferably has an aluminosilicate skeleton or a silicoaluminophosphate skeleton. More preferably, the small pore molecular sieve has an aluminosilicate backbone (ie, the first molecular sieve is a zeolite), especially when the small pore molecular sieve has a framework type which is STI, AEI, CHA, or AEI-CHA intergrowth, especially AEI or CHA, is.

In a second molecular sieve catalyst embodiment, the first molecular sieve has a framework type selected from the group consisting of AEI, MFI, EMT, ERI, MOR, FER, BEA, FAU, CHA, LEV, MWW, CON, and EUO, and mixtures of any two or more thereof.

In a third molecular sieve catalyst embodiment, the first molecular sieve is a medium pore molecular sieve. The medium pore molecular sieve preferably has a framework type selected from the group consisting of MFI, FER, MWW and EUO, more preferably MFI.

In a fourth molecular sieve catalyst embodiment, the first molecular sieve is a large pore molecular sieve. The large pore molecular sieve preferably has a framework type selected from the group consisting of CON, BEA, FAU, MOR and EMT, more preferably BEA.

In each of the first to fourth molecular sieve catalyst embodiments, the first molecular sieve preferably comprises an aluminosilicate backbone (e.g., the first molecular sieve is a zeolite). Each of the aforementioned three letter codes represents a skeleton type in accordance with the IUPAC Commission on Zeolite Nomenclature and / or the Structure Commission of the International Zeolite Association.

In any of the first to fourth molecular sieve catalyst embodiments, it may be generally preferred that the first molecular sieve (e.g., large pore, medium pore, or small pore) has a framework that is not an intergrowth of at least two different framework types.

The first molecular sieve typically has a silica to alumina molar ratio (SAR) of 10 to 200 (e.g., 10 to 40), such as 10 to 100, more preferably 15 to 80 (e.g., 15 to 30). The SAR generally refers to a molecule having an aluminosilicate backbone (e.g., a zeolite) or a silicoaluminophosphate backbone, preferably an aluminosilicate backbone (e.g., a zeolite).

The molecular sieve catalyst of the first, third and fourth molecular sieve catalyst embodiments (and also for some of the skeletal types of the second molecular sieve catalyst embodiment) can, especially if the first molecular sieve is a zeolite, have an infrared spectrum with a characteristic absorption peak in the range of 750 cm ^-1 to 1050 cm ^-1 (in addition to the absorption peaks for the molecular sieve itself). Preferably, the characteristic absorption peak is in the range of 800 cm ^-1 to 1000 cm ^-1 , more preferably in the range of 850 cm ^-1 to 975 cm ^-1 .

It has been found that the molecular sieve catalyst of the first molecular sieve catalyst embodiment has a favorable passive NO _x adsorber (PNA) activity. The molecular sieve catalyst may be used to store NO _x when the exhaust gas temperatures are relatively cool, such as shortly after starting a lean burn engine. The NO _x storage by the molecular sieve catalyst takes place at low temperatures (eg less than 200 ° C). As the lean-mixture engine warms up, the exhaust gas temperature rises and the temperature of the molecular sieve catalyst also increases. The molecular sieve catalyst releases adsorbed NO _x at these higher temperatures (eg, 200 ° C or above).

It has also been unexpectedly found that the molecular sieve catalyst, particularly the molecular sieve catalyst of the second molecular sieve catalyst embodiment, has cold start catalyst activity. Such activity may reduce emissions during the cold start period by adsorbing NO _x and hydrocarbons (HCs) at relatively low exhaust gas temperatures (eg, less than 200 ° C). The adsorbed NO _x and / or the adsorbed HCs can be released when the Temperature of the molecular sieve catalyst is near or above the effective temperature of the other catalyst components or emission control devices for oxidizing NO and / or HCs.

The second region comprises a nitrogen dioxide reducing material comprising at least one inorganic oxide. The at least one inorganic oxide is preferably an oxide of the 2nd, 3rd, 4th, 5th, 13th and 14th group of the elements. The at least one inorganic oxide is preferably selected from the group consisting of alumina, ceria, magnesia, silica, titania, zirconia, niobium oxide, tantalum oxides, molybdenum oxides, tungsten oxides, and mixed oxides or composite oxides thereof. Most preferably, the at least one inorganic oxide comprises alumina, ceria or a magnesia / alumina composite oxide. A particularly preferred inorganic oxide is alumina. In embodiments wherein the at least one inorganic oxide comprises alumina, the at least one inorganic oxide may consist essentially of alumina, and more preferably may be alumina.

Another particularly preferred inorganic oxide is a mixture of silica and alumina, preferably in a mass ratio of between 1:10 and 10: 1, more preferably in a mass ratio of 1: 5 to 5: 1, more preferably in a mass ratio of 1: 2 to 2: 1, eg 1: 1.

The inorganic oxide preferably does not have an activity as a selective catalytic reduction (SCR) catalyst. Thus, in catalyzing the reduction of NO _x , eg, NO ₂ , with a nitrogen-containing reducing agent, such as ammonia or a precursor thereof, or with a hydrocarbon reducing agent, such as fuel from an internal combustion engine, the inorganic oxide is preferably not significantly catalytically active. The inorganic oxide is preferably not selected from the group consisting of an oxide or oxides of chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel ( Ni), titanium (Ti), tungsten (W), vanadium (V), or a combination of any two or more thereof, and is more preferably not an oxide or oxides of titanium (Ti), tungsten (W), vanadium ( V) selected.

The at least one inorganic oxide may further additionally or alternatively comprise a second molecular sieve.

The second molecular sieve is typically composed of aluminum, silicon and / or phosphorus. The molecular sieve generally has a three-dimensional arrangement (eg a framework) of SiO ₄ , AlO ₄ and / or PO ₄ , which are linked together by common oxygen atoms. The molecular sieve may have an anionic skeleton. The charge of the anionic skeleton may be balanced by cations, such as by cations of the alkali and / or alkaline earth elements (eg Na, K, Mg, Ca, Sr and Ba), ammonium cations and / or protons.

Typically, the second molecular sieve comprises an aluminosilicate backbone, an aluminophosphate backbone or a silicoaluminophosphate backbone. The second molecular sieve may comprise an aluminosilicate skeleton or an aluminophosphate skeleton. It is preferable that the second molecular sieve has an aluminosilicate skeleton or a silicoaluminophosphate skeleton. More preferably, the second molecular sieve has an aluminosilicate skeleton.

When the second molecular sieve has an aluminosilicate backbone, the molecular sieve is preferably a zeolite.

The second molecular sieve may consist of a small pore molecular sieve (ie, a molecular sieve having a maximum ring size of eight tetrahedral atoms), a medium pore molecular sieve (ie, a molecular sieve having a maximum ring size of ten tetrahedral atoms) and a large pore molecular sieve (ie, a molecular sieve having a maximum ring size of twelve tetrahedral atoms). More preferably, the second molecular sieve is selected from a small pore molecular sieve and a medium pore molecular sieve.

In a preferred embodiment, the second molecular sieve is a small pore molecular sieve. The small pore molecular sieve preferably has a framework type selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, STI, THO, TSC, UEI, UFI, VNI, YUG and ZON and a mixture or an intergrowth of any two or more thereof. The adhesion is preferably from KFI-SIV, ITE-RTH, AEW-UEI, AEI-CHA and AEI-SAV selected. More preferably, the small pore molecular sieve has a framework type which is STI, AEI, CHA or AEI-CHA intergrowth. Even more preferably, the small pore molecular sieve has a framework type which is AEI or CHA, especially AEI.

The small-pore molecular sieve preferably has an aluminosilicate skeleton or a silicoaluminophosphate skeleton. More preferably, the small pore molecular sieve has an aluminosilicate backbone (ie, the second molecular sieve is a zeolite), especially when the small pore molecular sieve has a framework type which is STI, AEI, CHA, or an AEI-CHA intergrowth, especially AEI or CHA, is.

In another preferred embodiment, the second molecular sieve has a framework type selected from the group consisting of AEI, MFI, EMT, ERI, MOR, FER, BEA, FAU, CHA, LEV, MWW, CON, and EUO, as well as mixtures of any two or more thereof.

In a further preferred embodiment, the second molecular sieve is a medium pore molecular sieve. The medium pore molecular sieve preferably has a framework type selected from the group consisting of MFI, FER, MWW and EUO, more preferably MFI.

In a further preferred embodiment, the second molecular sieve is a large-pore molecular sieve. The large pore molecular sieve preferably has a framework type selected from the group consisting of CON, BEA, FAU, MOR and EMT, more preferably BEA.

In each of the aforementioned embodiments, the second molecular sieve preferably comprises an aluminosilicate backbone (e.g., the molecular sieve is a zeolite). Each of the aforementioned three letter codes represents a skeleton type in accordance with the IUPAC Commission on Zeolite Nomenclature and / or the Structure Commission of the International Zeolite Association.

In any of the foregoing embodiments, it may be generally preferred that the second molecular sieve (e.g., large pore, medium pore, or small pore) have a framework that is not an intergrowth of at least two different framework types.

The second molecular sieve typically has a silica to alumina molar ratio (SAR) of 10 to 200 (e.g., 10 to 40), such as 10 to 100, more preferably 15 to 80 (e.g., 15 to 30). The SAR generally refers to a molecule having an aluminosilicate backbone (e.g., a zeolite) or a silicoaluminophosphate backbone, preferably an aluminosilicate backbone (e.g., a zeolite).

The second molecular sieve preferably does not comprise copper (Cu) or iron (Fe). It is particularly preferred that the second molecular sieve has no activity as a selective catalytic reduction (SCR) catalyst. Thus, preferably, the second molecular sieve is not significantly catalytically active in catalyzing the reduction of NO _x , eg NO ₂ , with a nitrogen containing reductant, such as ammonia or a precursor thereof, or with a hydrocarbon reductant, such as fuel from an internal combustion engine ,

Preferred first inorganic oxides preferably have a surface area in the range of 10 to 1500 m ² / g, pore volumes in the range of 0.1 to 4 mL / g, and pore diameters of about 10 to 1000 angstroms. High surface area inorganic oxides having a surface area greater than 80 m ² / g are particularly preferred, for example, high surface area ceria or alumina. Other preferred first inorganic oxides include magnesia / alumina composite oxides, which optionally further comprise a cerium-containing component, eg, ceria. In such cases, the ceria may be present on the surface of the magnesia / alumina composite oxide, eg in the form of a coating.

Preferably, the at least one inorganic oxide comprises an inorganic oxide doped with a dopant, the dopant being an element selected from the group consisting of tungsten (W), silicon (Si), titanium (Ti), lanthanum (La). , Praseodymium (Pr), hafnium (Hf), yttrium (Y), ytterbium (Yb), samarium (Sm), neodymium (Nd), and a combination of two or more thereof or an oxide thereof.

The NO _x absorber catalyst of the invention may have one of several arrangements that can facilitate the storage and release of NO _x and provide a broader temperature window for NO _x storage and release.

In a first arrangement, the NO _x absorber catalyst comprises or consists essentially of or consists of the first region and the second region.

An example of a first arrangement of the NO _x absorber catalyst is shown in FIG 1 illustrated. In the in 1 As shown, the NO _x absorber catalyst comprises a first zone and a second zone.

The first region (1) may be disposed or supported on the substrate (3). It is preferred that the first region be directly disposed on the substrate or directly supported (i.e., the first region is in direct contact with the surface of the substrate).

In the first arrangement, the first region may be a first zone. The first zone typically has a length of 10 to 90% of the length of the substrate (eg 10 to 45%), preferably 15 to 75% of the length of the substrate (eg 15 to 40%), more preferably 20 to 70% (eg 30 to 65%, such as 25 to 45%), more preferably 25 to 65% (eg 35 to 50%) of the length of the substrate.

In the first arrangement, the second region (2) may be a second zone. The second zone typically has a length of 10 to 90% of the length of the substrate (eg 10 to 45%), preferably 15 to 75% of the length of the substrate (eg 15 to 40%), more preferably 20 to 70% (eg 30 to 65%, such as 25 to 45%), more preferably 25 to 65% (eg 35 to 50%) of the length of the substrate.

The first zone may be located upstream of the second zone. Alternatively, the first zone may be located downstream of the second zone. It is preferred that the second zone, as in 1 shown, is arranged upstream of the first zone.

The first zone comprises or consists essentially of a NO _x absorber material comprising a molecular sieve catalyst. The second zone comprises or consists essentially of a nitrogen dioxide reducing material comprising at least one inorganic oxide.

When the first zone is disposed upstream of the second zone, the first zone may be disposed at an inlet end of the substrate and / or the second zone may be disposed at an outlet end of the substrate.

When the first zone is located downstream of the second zone, the first zone may be disposed at an outlet end of the substrate and / or the second zone may be disposed at an inlet end of the substrate.

The first zone may be adjacent to the second zone. Preferably, the first zone is in contact with the second zone.

When the first zone is adjacent to the second zone and / or is in contact with the second zone, the combination of the first zone and the second zone may be disposed or supported on the substrate in the form of a layer (eg, a single layer) , Thus, a layer (e.g., a single layer) may be formed on the substrate when the first and second zones are adjacent to or in contact with each other. Such an arrangement can avoid backpressure problems.

Typically, the first zone and / or the second zone are disposed or supported on the substrate. Preferably, the first zone and / or the second zone are directly disposed on the substrate (i.e., the first zone and / or the second zone is in contact with a surface of the substrate).

In a second arrangement, the NO _x absorber catalyst comprises a first region and a second region. The first region comprises or consists essentially of a NO _x absorber material comprising a molecular sieve catalyst. The second region comprises or consists essentially of a nitrogen dioxide reducing material comprising at least one inorganic oxide. In the second arrangement, either the first region overlaps the second region (see, for example, FIG 2 ) or the second region overlaps the first region (see for example 3 ).

1. (a) auf der zweiten Region angeordnet oder geträgert sein; und/oder
2. (b) direkt auf dem Substrat angeordnet sein [d.h. die erste Region befindet sich in Kontakt mit einer Oberfläche des Substrats]; und/oder
3. (c) sich in Kontakt mit der zweiten Region befinden [d.h. die erste Region ist benachbart zu der zweiten Region oder grenzt an die zweite Region an].

The second region may be disposed directly on the substrate (ie, the second region is in contact with a surface of the substrate). The first region can:

1. (a) be located or carried on the second region; and or
2. (b) be placed directly on the substrate [ie, the first region is in contact with a surface of the substrate]; and or
3. (c) be in contact with the second region [ie the first region is adjacent to the second region or is adjacent to the second region].

A portion or region of the first region may be located or carried on the second region (eg, the first region may overlap the second region); see for example the in 2 illustrated arrangement. The second region may be a second zone and the first region may be a first layer or a first zone.

When a part or area of the first region is located or supported on the second region, it is preferable that the part or area of the first region is located directly on the second region (i.e., the first region is in contact with a surface of the second region).

Alternatively, a portion or region of the second region may be located or carried on the first region (eg, the second region may overlap the first region); see for example the in 3 illustrated arrangement. The first region may be a first zone and the second region may be a second layer or a second zone.

When a part or region of the second region is located or carried on the first region, it is preferable that the part or region of the second region is located directly on the first region (i.e., the second region is in contact with a surface of the first region).

In the second arrangement, the first region may be located upstream of the second region. For example, the first region may be disposed at an inlet end of the substrate and the second region may be disposed at an outlet end of the substrate.

Alternatively, the first region may be located downstream of the second region. For example, the first region may be disposed at an outlet end of the substrate and the second region may be disposed at an inlet end of the substrate.

In the second arrangement, the second region may be a second layer and the first region may be a first zone with the first zone disposed on the second layer. Preferably, the first zone is disposed directly on the second layer (i.e., the first zone is in contact with a surface of the second layer). Alternatively, the first region may be a first layer and the second region may be a second zone with the second zone disposed on the first layer. Preferably, the second zone is disposed directly on the first layer (i.e., the second zone is in contact with a surface of the first layer).

When the first zone is disposed or supported on the second layer, it is preferable that the entire length of the first zone is disposed or supported on the second layer. The length of the first zone is less than the length of the second layer. It is preferable that the first zone is disposed on the second layer at an outlet end of the substrate.

When the second zone is disposed or supported on the first layer, it is preferred that the entire length of the second zone be disposed or supported on the first layer. The length of the second zone is less than the length of the first layer. It is preferable that the second zone is disposed on the first layer at an inlet end of the substrate.

In a third arrangement, the NO _x absorber catalyst comprises a first layer and a second layer. The first layer comprises or consists essentially of a NO _x absorber material comprising a molecular sieve catalyst. The second layer comprises or consists essentially of a nitrogen dioxide reducing material comprising at least one inorganic oxide.

The first layer can be arranged on the second layer, preferably arranged directly thereon (see, for example, those in US Pat 4 shown arrangement). The second layer may be disposed on the substrate. Preferably, the second layer is disposed directly on the substrate.

Alternatively, the second layer can be arranged on the first layer, preferably arranged directly thereon (see, for example, FIGS 5 shown arrangement). The first layer may be disposed on the substrate. Preferably, the first layer is disposed directly on the substrate. This example of the third arrangement, ie the in 5 shown arrangement is particularly preferred.

The first to third arrangement of the NO _x absorber catalyst of the invention may be advantageous when the nitrogen dioxide reducing material comprising at least one inorganic oxide is arranged to react with all or most of any inlet exhaust gas before the NO _x absorber material comprising a molecular sieve catalyst (eg, when the nitrogen dioxide reduction material comprising at least one inorganic oxide is upstream of the NO _x absorbent material comprising a molecular sieve catalyst and / or in a layer over the NO _x absorbent material comprising a molecular sieve catalyst). Without wishing to be bound by theory, it is believed that the nitrogen dioxide reducing material partially reduces NO ₂ to NO, resulting in a surprisingly improved NO _X storage efficiency in the first region due to the increased affinity of NO for the NO _x comprising a molecular sieve catalyst Absorbent material leads. As a result, the catalyst as a whole has improved NO _x storage properties and a higher NO _x release temperature. This effect is surprising since it is generally believed in the art that NO _x storage efficiency is improved by increasing the amount of NO _{2 present} , eg by oxidation of NO to NO ₂ .

The NO _x absorber catalyst of the invention may therefore be advantageous in certain applications, for example, where the NO _x absorber catalyst is located upstream of an SCR or SCRF ™ catalyst. In such arrangements, it may be advantageous if the NO _x release temperature of the NO _x adsorber catalyst of the invention is higher than conventional NO _x absorber catalysts to ensure that NO _{x is} not released from the NO _x absorber catalyst until the NO _x release catalyst downstream SCR or SCRF ™ catalyst at a temperature high enough to be catalytically active for the reduction of NO _x to N ₂ . Thus, the NO _x adsorbent catalyst of the invention may be particularly advantageous in reducing NO _x emissions from an exhaust gas stream, eg, an exhaust gas stream from a lean burn engine, such as a diesel engine (preferably a light duty diesel engine).

To avoid misunderstanding, it should be noted that the first region is different from the second region (i.e., has a different composition).

With reference to the first and second arrangements, generally, when the first region is a first zone, the first zone typically has a length of 10% to 90% of the length of the substrate (eg, 10 to 45%), preferably 15 to 75% of the substrate Length of the substrate (eg 15 to 40%), more preferably 20 to 70% (eg 30 to 65%, such as 25 to 45%) of the length of the substrate, even more preferably 25 to 65% (eg 35 to 50%) of the Length of the substrate.

In general, when the second region is a second zone, the second zone is 10 to 90% of the length of the substrate (eg, 10 to 45%), preferably 15 to 75% of the length of the substrate (eg, 15 to 40%). more preferably 20 to 70% (eg 30 to 65%, such as 25 to 45%), even more preferably 25 to 65% (eg 35 to 50%) of the length of the substrate.

In the first to third arrangements, when the first region is a first layer, the first layer typically extends the full length (i.e., substantially the entire length) of the substrate, particularly the entire length of the channels of a substrate monolith.

In general, when the second region is a second layer, typically the second layer extends the full length (i.e., substantially the entire length) of the substrate, particularly the entire length of the channels of a substrate monolith.

In the first to third arrangements, the first region is preferably substantially free of or substantially consists of rhodium and / or a NO _x storage component comprising or consisting essentially of an oxide, a carbonate or a hydroxide of an alkali metal, an alkaline earth metal and / or a rare earth metal , More preferably, the first region does not comprise rhodium and / or an NO _x storage component comprising or consisting essentially of an oxide, a carbonate or a hydroxide of an alkali metal, an alkaline earth metal and / or a rare earth metal. Thus, the first region is preferably not a lean NO _x trap (LNT) region (ie, no region having a lean NO _x trap activity).

Additionally or alternatively, in the first to third arrangements, the second region is preferably substantially free of rhodium and / or a NO _x storage component comprising an oxide, a carbonate or a hydroxide of an alkali metal, an alkaline earth metal and / or a rare earth metal (except an oxide of cerium (ie, the second NO _x absorbent material)) or consists essentially thereof. More preferably, the second region does not comprise rhodium and / or a NO _x storage component comprising an oxide, a carbonate or a hydroxide of an alkali metal, an alkaline earth metal and / or a rare earth metal (except for an oxide of cerium (ie, the second NO _x Absorbent material)) or consists essentially thereof. Thus, the second region is preferably not a lean NO _x trap (LNT) region (ie, no region having a lean NO _x trap activity).

Additionally or alternatively, in the first to third arrangements, the second region is substantially free of platinum group metals (PGMs). Thus, the second region may preferably be a PGM-free region, ie a PGM-free zone or a PGM-free layer. Without wishing to be bound by theory, it is believed that the absence of PGMs in the second region facilitates the nitrogen dioxide reduction properties of the inorganic oxide by excluding catalytic metals that can catalyze the oxidation of NO to NO ₂ .

In a fourth arrangement of the invention, the NO _x absorber catalyst has an arrangement as defined in any one of the above-described first to third arrangements, and further comprises a diesel oxidation catalyst (DOC) region. The DOC region has a diesel oxidation catalyst activity. Thus, the DOC region is capable of oxidizing carbon monoxide (CO) and / or hydrocarbons (HCs) and optionally nitrogen monoxide (NO).

The DOC region can be a DOC zone. The DOC zone typically has a length of 10 to 90% (eg 10 to 45%) of the length of the substrate, preferably 15 to 75% of the length of the substrate (eg 15 to 40%), more preferably 20 to 60% (eg 30 to 55% or 25 to 45%), more preferably 25 to 50% (eg 25 to 40%) of the length of the substrate.

The DOC region is preferably located upstream of the first region and the second region. It is preferable that the DOC region is disposed at an inlet end of the substrate. More preferably, the DOC region is a DOC zone disposed at an inlet end of the substrate.

Alternatively, the DOC region may be a DOC layer. The DOC layer may extend the full length (i.e., substantially the entire length) of the substrate, particularly the entire length of the channels of a substrate monolith.

The DOC layer is preferably disposed on the first region and the second region. Thus, the DOC layer in front of the first region and the second region comes into contact with an inlet exhaust gas.

In a particularly preferred example of the fourth arrangement, the DOC region (4) is a DOC layer or a DOC zone, preferably a DOC layer, which comprises on a second layer comprising a nitrogen dioxide reduction material comprising at least one inorganic oxide, is disposed (preferably disposed directly thereon), and the second layer is disposed on (preferably directly disposed on) a first layer comprising a NO _x absorber material comprising a molecular sieve catalyst. The first layer is disposed on a substrate (preferably disposed directly thereon). This preferred arrangement is in 6 shown.

In a further preferred example of the fourth arrangement, the DOC region (4) is a DOC or DOC zone, preferably a DOC layer, on at least a portion or a portion of both the first region and the second region as hereinbefore described (preferably disposed directly thereon). In a particularly preferred example, the DOC region is a DOC layer disposed on (preferably disposed directly on) a first layer, the first layer comprising a first region and a second region. In such an arrangement, the first region (ie, a first region comprising a molecular sieve catalyst comprising NO _x absorbent material) is disposed downstream of the second region (ie, a second region comprising a nitrogen dioxide reducing material comprising at least one inorganic oxide). The first region and the second region are both disposed on a substrate (preferably disposed directly thereon). This preferred arrangement is in 7 and 8th shown.

To avoid misunderstandings, it should be noted that in 7 and 8th As shown, the DOC region may be a layer and / or a zone as previously described.

In the 7 The arrangement shown in which the second region is located upstream of the first region is particularly preferred.

The NO _x absorber catalyst of the present invention, including any one of the first to fourth arrangements, preferably does not include an SCR catalyst (eg, a region comprising an SCR catalyst), particularly not an SCR catalyst comprising a metal comprising composed of cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), tungsten (W), vanadium (V ) or a combination of any two or more thereof.

The regions, zones, and layers described hereinabove can be prepared using conventional methods of making and applying washcoats to a substrate, which are also known in the art (see, for example, our US Pat WO 99/47260 . WO 2007/077462 and WO 2011/080525 ).

The first region of the first to fourth assemblies typically comprises a total loading of noble metal (ie, the noble metal of the molecular sieve catalyst in the first region) of 5 to 550 g ft ^-3 , preferably 15 to 400 g ft ^-3 (eg 75 to 350 g ft ^{). 3} ), more preferably 25 to 300 g ft ^-3 (eg 50 to 250 g ft ^-3 ), even more preferably 30 to 150 g ft ^-3 .

The NO _x absorber catalyst of the invention comprises a substrate having an inlet end and an outlet end.

The substrate typically has a plurality of channels (e.g., for passing the exhaust gas). In general, the substrate is a ceramic material or a metallic material.

It is preferable that the substrate be made of cordierite (SiO ₂ -Al ₂ O ₃ -MgO), silicon carbide (SiC), Fe-Cr-Al alloy, Ni-Cr-Al alloy, or stainless steel alloy or composite.

Typically, the substrate is a monolith (also referred to herein as a substrate monolith). Such monoliths are well known in the art. The substrate monolith may be a flow through monolith or a filter monolith.

A flow-through monolith typically comprises a honeycomb monolith (e.g., a metallic or ceramic honeycomb monolith) having a plurality of channels extending therethrough, each channel being open at the inlet end and at the outlet end.

A filter monolith generally includes a plurality of inlet channels and a plurality of outlet channels, wherein the inlet channels are open at an upstream end (ie, the exhaust inlet side) and plugged or occluded at a downstream end (ie, the exhaust outlet side) that blocks outlet channels at an upstream end or are closed and open at a downstream end, and wherein each inlet channel is separated from an outlet channel by a porous structure.

When the monolith is a filter monolith, it is preferred that the filter monolith be a wall-flow filter. In a wall-flow filter, each inlet channel is alternately separated from an outlet channel by a wall of the porous structure, and vice versa. It is preferred that the inlet channels and the outlet channels are arranged in a honeycomb arrangement. When there is a honeycomb arrangement, it is preferred that the channels that are vertically and laterally adjacent to an inlet channel are clogged at an upstream end and vice versa (i.e., the channels adjacent vertically and laterally to an outlet channel are clogged at a downstream end). When viewed from either end, the alternately closed and open ends of the channels have the appearance of a chessboard.

In principle, the substrate may have any shape or size. However, the shape and size of the substrate are usually selected to optimize the exposure of the exhaust gas to the catalytically active materials in the catalyst. The substrate may, for example, have a tubular, fibrous or particulate shape. Examples of suitable carrier substrates include a substrate monolithic cordierite honeycomb type, a SiC honeycomb type substrate, a stratified or knitted type substrate, a foam type substrate, a transverse flow type substrate, a metal wire mesh type substrate, a porous metal body type substrate, and a ceramic particle type substrate.

The substrate may be an electrically heatable substrate (ie, the electrically heatable substrate is a common electrically heating substrate). When the substrate is an electrically heatable substrate, the NO _x absorber catalyst of the invention comprises an electrical power connection, preferably at least two electrical power connections, more preferably only two electrical power connections. Each electrical power connection may be electrically connected to an electrically heatable substrate and an electrical power source. The NO _x absorber catalyst can be heated by ohmic heating (joule heating) in which an electric current converts electrical energy into heat energy through an (electrical) resistance.

The electrically heatable substrate may be used for releasing any stored NO _x from the first region. Thus, when the electrically heatable substrate is turned on, the NO _x absorber catalyst is heated and the temperature of the molecular sieve catalyst can be brought to its NO _x release temperature. Examples of suitable electrically heatable substrates are in US 4,300,956 . US 5,146,743 and US Pat. No. 6,513,324 described.

In general, the electrically heatable substrate comprises a metal. The metal may be electrically connected to the electrical power connection or the electrical power connections.

Typically, the electrically heatable substrate is an electrically heatable honeycomb substrate. The electrically heatable substrate may be a conventional electrically heatable honeycomb substrate.

The electrically heatable substrate may comprise an electrically heatable substrate monolith (e.g., a metal monolith). The monolith may comprise a sheet or sheet of corrugated metal. The sheet or sheet of corrugated metal may be rolled, wrapped or stacked. When the sheet of corrugated metal is rolled or wound, it may be rolled or wound into a coil, spiral or concentric pattern.

The metal of the electrically heatable substrate, the metal monolith, and / or the corrugated metal sheet or sheet may comprise a ferritic, aluminum-comprising steel such as Fecralloy ™.

Typically, the NO _x absorber catalyst releases NO _x at a temperature greater than 200 ° C. This is the lower limit of the second temperature range. Preferably, the NO _x absorber catalyst releases NO _x at a temperature of 220 ° C or above, such as 230 ° C or above, 240 ° C or above, 250 ° C or above, or 260 ° C or above.

The NO _x absorber catalyst typically absorbs or stores NO _x at a temperature of 250 ° C or below. This is the upper limit of the first temperature range. Preferably, the NO _x absorber catalyst absorbs or stores NO _x at a temperature of 220 ° C or below, such as 200 ° C or below, 190 ° C or below, 180 ° C or below, or 175 ° C or below.

The NO _x absorber catalyst may preferably absorb or store nitrogen monoxide (NO). Thus, any reference to absorbing, storing or releasing NO _X in this context may refer to adsorbing, storing or releasing nitric oxide (NO). Preferred absorption or storage of NO reduces the ratio of NO: NO ₂ in the exhaust gas.

The invention also provides an exhaust system comprising the NO _x absorber catalyst and an emission control device. Examples of an emission control device comprising a diesel particulate filter (DPF), a lean NO _x trap (LNT), a lean _NOx catalyst (LNC), a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF ™) catalyst, an ammonia slip or ammonia blocking catalyst (ASC) and combinations of two or more thereof. Such emission control devices are all well known in the art.

It is preferred that the exhaust system comprises an emission control device that is selected from the group _X trap from a lean NO (LNT), an ammonia-slip catalyst (ASC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR) catalyst, a catalyzed soot filter (CSF), a selective catalytic reduction filter (SCRF ™) catalyst and combinations of two or more thereof. More preferably, the emissions control device is selected from the group consisting of a lean NO _x trap (LNT), a selective catalytic reduction (SCR) catalyst, a selective catalytic reduction filter (SCRF ™) catalyst, and combinations of two or three more of this exists.

In a preferred exhaust system of the invention, the emission control device is an LNT. The NO _x release temperature of the NO _x absorber catalyst of the invention may overlap with a NO _x storage temperature of an LNT. The NO _x absorber catalyst of the invention may be used in conjunction with an LNT and an SCR or SCRF ™ catalyst (eg, an exhaust system comprising a PNA + LNT + SCR or SCRF ™, in that order) by a wide range provide temperature window for the storage and treatment of NO _X.

In general, the exhaust system according to the invention may further comprise means for introducing hydrocarbon into the exhaust gas.

The means for introducing hydrocarbon into the exhaust gas may comprise or consist of a hydrocarbon feed device (eg for producing a rich exhaust gas). The hydrocarbon feed device may be electronically coupled to an engine management system configured to inject hydrocarbon into the exhaust gas, typically to release NO _x (eg, stored NO _x ) from an LNT.

The hydrocarbon feed device may be an injector. The hydrocarbon feed device or injector is suitable for injecting fuel into the exhaust gas. The hydrocarbon feed device is typically located downstream of the exhaust gas outlet of the lean burn engine. The hydrocarbon feed device may be located upstream or downstream of the NO _x absorber catalyst of the present invention.

Alternatively or in addition to the hydrocarbon feed device, the lean burn engine may include an engine management system (eg, an engine control unit [ECU]). The engine management system may be configured to inject the hydrocarbon (eg, fuel) into the cylinder, typically to release NO _X (eg, stored NO _X ) from an LNT.

Generally, the engine management system is coupled to a sensor in the exhaust system that monitors the status of an LNT. Such a sensor may be located downstream of the LNT. The sensor can monitor the NO _x composition of the exhaust gas at the outlet of the LNT.

In general, the hydrocarbon is a fuel, preferably diesel fuel. When the hydrocarbon is a fuel, e.g. Diesel fuel, it is preferred that the fuel comprise ≤50ppm sulfur, more preferably ≤15ppm sulfur, such as ≤10ppm sulfur, and even more preferably ≤5ppm sulfur.

In the first to fourth arrangements of the NO _x absorber catalyst of the invention, the hydrocarbon feed device may be disposed upstream of the NO _x absorber catalyst of the invention.

When the exhaust system of the present invention comprises an SCR catalyst or a SCRF ™ catalyst, the exhaust system may further include an injector for injecting a nitrogen-containing reducing agent such as ammonia, or an ammonia precursor such as urea or ammonium formate, preferably urea, into the exhaust downstream of Oxidation catalyst and upstream of the SCR catalyst or the SCRF ™ catalyst include. Such an injector may be fluidly connected to a source (e.g., a tank) of a precursor of nitrogen containing reductant. Valve-controlled metering of the precursor into the exhaust may be controlled by suitably programmed engine management means and closed loop or open loop feedback provided by sensors monitoring the composition of the exhaust gas. Ammonia may also be generated by heating ammonium carbamate (a solid) and the generated ammonia may be injected into the exhaust gas.

Alternatively, or in addition to the injector for injecting a nitrogen-containing reductant, ammonia may be generated in situ (eg, during a rich regeneration of an upstream SCR catalyst). Catalytic converter or SCRF ™ catalyst (for example, if the exhaust system further comprises a hydrocarbon feed device, such as an engine management system, for injecting a hydrocarbon into the cylinder to release NO _x (eg, stored NO _x )). is configured from an LNT.

The SCR catalyst or SCRF ™ catalyst may comprise a metal selected from the group consisting of at least one (metal) of Cu, Hf, La, Au, In, V, lanthanides and Group VIII transition metals (eg Fe), wherein the metal is supported on a refractory oxide or molecular sieve. The metal is preferably selected from Ce, Fe, Cu and combinations of any two or more thereof, more preferably the metal is Fe or Cu.

The refractory oxide for the SCR catalyst or the SCRF ™ catalyst may be selected from the group consisting of Al ₂ O ₃ , TiO ₂ , CeO ₂ , SiO ₂ , ZrO ₂ and mixed oxides containing two or more thereof , The non-zeolite catalyst may further comprise tungsten oxide (eg, V ₂ O ₅ / WO ₃ / TiO ₂ , WO _X / CeZrO ₂ , WO _X / ZrO ₂ or Fe / WO _X / ZrO ₂ ).

It is particularly preferred if an SCR catalyst, a SCRF ™ catalyst or a washcoat thereof comprises at least one molecular sieve, such as an aluminosilicate zeolite or a SAPO. The at least one molecular sieve may be a small pore, a medium pore or a large pore molecular sieve. By "small pore molecular sieve" herein we mean molecular sieves containing a maximum ring size of 8, such as CHA; By "medium pore molecular sieve" herein we mean a molecular sieve containing a maximum ring size of 10, such as ZSM-5; and by "large pore molecular sieve" we mean herein a molecular sieve having a maximum ring size of 12, such as beta. Small pore molecular sieves may be advantageous for use in SCR catalysts.

Preferred molecular sieves for an SCR catalyst or SCRF ™ catalyst are synthetic aluminosilicate zeolite molecular sieves selected from the group consisting of AEI, ZSM-5, ZSM-20, ERI including ZSM-34, mordenite, ferrierite, BEA, inclusive Beta, Y, CHA, LEV including Nu-3, MCM-22 and EU-1, preferably AEI or CHA, and having a silica to alumina ratio of about 10 to about 50, such as about 15 to about 40.

In a first exhaust system embodiment of the invention, the exhaust system comprises the NO _x absorber catalyst of the present invention (including any one of the first to fourth arrangements of the NO _x absorber catalyst) and a lean NO _x trap (LNT) the NO _x absorber catalyst separate substrate]. Such an arrangement may be referred to as PNA / LNT. The NO _x adsorbent catalyst is typically followed by the lean NO _x trap (LNT) (eg, the NO _x absorber catalyst is upstream of the lean NO _x trap (LNT)). Thus, for example, an outlet of the NO _x absorber catalyst is connected to an inlet of the lean NO _x trap (LNT), preferably connected directly (eg, without an intervening emission control device). There may be a hydrocarbon feed device between the NO _x absorber catalyst and the LNT.

A second exhaust system embodiment relates to an exhaust system comprising the NO _x absorber catalyst of the present invention (including any of the first to fourth locations of the NO _x absorber catalyst) and a selective catalytic reduction (SCR) catalyst. Such an arrangement may be referred to as PNA / SCR. The NO _x absorber catalyst is typically followed by the selective catalytic reduction (SCR) catalyst (eg, the NO _x absorber catalyst is located upstream of the selective catalytic reduction (SCR) catalyst). Thus, for example, an outlet of the NO _x absorber catalyst is connected to an inlet of the SCR catalyst, preferably connected directly (eg, without an intervening emission control device).

An injector of a nitrogen-containing reducing agent may be disposed between the NO _x absorber catalyst and the selective catalytic reduction (SCR) catalyst. Thus, the NO _x absorber catalyst may be followed by an injector of a nitrogen-containing reducing agent (eg, the NO _x absorber catalyst is disposed upstream of an injector of nitrogen-containing reducing agent) and the injector of a nitrogen-containing reducing agent may be followed by the selective catalytic reduction (SCR) catalyst (eg Injector of a nitrogen-containing reducing agent upstream of the selective catalytic reduction (SCR) catalyst arranged).

In the second exhaust system embodiment, it may be preferred that the substrate (eg, the NO _x absorber catalyst) is a filter monolith. It is particularly preferred that the substrate (eg, the NO _x absorber catalyst) is a filter monolith when the NO _x absorber catalyst comprises a DOC region.

A third exhaust system embodiment includes the NO _x absorber catalyst of the present invention (including any of the first to fourth locations of the NO _x absorber catalyst) and a selective catalytic reduction (SCRF ™) catalyst. Such an arrangement may be referred to as PNA / SCRF ™. The NO _x absorber catalyst is typically followed by the selective catalytic reduction (SCRF ™) catalyst (eg, the NO _x absorber catalyst is located upstream of the selective catalytic reduction (SCRF ™) catalyst). Thus, for example, an outlet of the NO _x absorber catalyst is connected to an inlet of the selective catalytic reduction filter (SCRF ™) catalyst, preferably connected directly (eg, without an intermediate emission control device).

An injector of a nitrogen-containing reductant may be disposed between the NO _x absorber catalyst and the selective catalytic reduction filter (SCRF ™) catalyst. Thus, the NO _x absorber catalyst may be followed by an injector of a nitrogen-containing reductant (eg, the NO _x absorber catalyst is disposed upstream of an injector of nitrogen-containing reductant), and the nitrogen-containing reductant injector may be followed by the SCRF ™ selective catalytic catalyst ( for example, the injector of a nitrogenous reductant is located upstream of the selective catalytic reduction (SCRF ™) catalyst.

A fourth exhaust system embodiment relates to an exhaust system comprising the NO _x absorber catalyst of the present invention (including any of the first to fourth locations of the NO _x absorber catalyst), a lean NO _x trap (LNT) and either a selective catalytic reduction (SCR ) Catalyst or a selective catalytic reduction filter (SCRF ™) catalyst. These arrangements may be referred to as a PNA / LNT / SCR arrangement or as a PNA / LNT / SCRF ™ arrangement. The NO _x absorber catalyst is typically followed by the lean NO _x trap (LNT) (eg, the NO _x absorber catalyst is located upstream of the lean NO _x trap (LNT)). The lean _NOx trap (LNT) typically follows either the selective catalytic reduction (SCR) catalyst or selective catalytic reduction filter (SCRF ™) catalyst (for example, the lean _NOx trap (LNT) upstream either the selective catalytic reduction (SCR) catalyst or the selective catalytic reduction filter (SCRF ™) catalyst arranged). There may be a hydrocarbon feed device between the NO _x absorber catalyst and the LNT.

An injector of a nitrogen-containing reductant may be disposed between the lean NO _x trap (LNT) and either the selective catalytic reduction (SCR) catalyst or the selective catalytic reduction filter (SCRF ™) catalyst. Thus, the lean NO _x trap (LNT) may be followed by an injector of nitrogen-containing reductant (eg, the lean NO _x trap (LNT) is disposed upstream of an injector of nitrogen-containing reductant) and the injector of a nitrogen-containing reductant may be selective catalytic reduction (SCR) catalyst or the selective catalytic reduction filter (SCRF ™) catalyst follow (eg, the injector of a nitrogen-containing reducing agent upstream of the selective catalytic reduction (SCR) catalyst or the selective catalytic reduction filter (SCRF ™) catalyst).

A fifth exhaust system embodiment relates to an exhaust system comprising the NO _x absorber catalyst of the invention (including any of the first to fourth locations of the NO _x absorber catalyst), a catalyzed soot filter (CSF), and a selective catalytic reduction (SCR) catalyst , Such an arrangement may be referred to as PNA / CSF / SCR. The NO _x absorber catalyst is typically followed by the catalyzed soot filter (CSF) (eg, the NO _x absorber catalyst is upstream of the catalyzed soot filter (CSF)). The catalyzed soot filter is typically followed by the selective catalytic reduction (SCR) catalyst (eg, the catalyzed soot filter is upstream of the selective catalytic reduction (SCR) catalyst).

An injector of a nitrogen-containing reducing agent may be disposed between the catalyzed soot filter (CSF) and the selective catalytic reduction (SCR) catalyst. Thus, the catalyzed soot filter (CSF) may be followed by an injector of nitrogen containing reductant (eg, the catalyzed soot filter (CSF) is upstream of an injector of nitrogen containing reductant) and the injector of a nitrogen containing reductant may be followed by the selective catalytic reduction (SCR) catalyst (eg For example, the injector of a nitrogen-containing reductant is upstream of the selective catalytic reduction (SCR) catalyst.

In any of the second through fifth embodiments of the exhaust system described hereinabove, an ASC catalyst may be disposed downstream of the SCR catalyst or the SCRF ™ catalyst (ie, in the form of a separate substrate monolith), or more preferably, a downstream or trailing zone End of the substrate monolith comprising the SCR catalyst can be used as a support for the ASC.

The exhaust system of the present invention (including the first to fifth exhaust system embodiments) may further include means for introducing hydrocarbon (eg, fuel) into the exhaust gas. When the means for introducing hydrocarbon into the exhaust gas is a hydrocarbon feed device, it is generally preferred that the hydrocarbon feed device is located downstream of the NO _x absorber catalyst of the present invention (unless otherwise noted above).

It may be preferred that the exhaust gas system according to the invention does not have a lean NO _x trap (LNT), in particular no lean NO _x trap (LNT) upstream of the NO _x absorber catalyst, such as, for example, directly upstream of the NO _x absorber catalyst (eg an intermediate emission control device).

The PNA activity of the NO _x absorber catalyst of the present invention allows NO _x , particularly NO, to be stored at low exhaust gas temperatures. At higher exhaust gas temperatures, the NO _x absorber catalyst is capable of oxidizing NO to NO ₂ . It is therefore advantageous to combine the NO _x absorber catalyst of the present invention with certain types of emission control devices as part of an exhaust system.

Another aspect of the invention relates to a vehicle or an apparatus. The vehicle or apparatus includes a lean burn engine. Preferably, the lean burn engine is a diesel engine.

The diesel engine may be a homogeneous compression ignition (HCCI) engine, a premixed charge compression ignition (PCCI) engine, or a low temperature combustion (LTC) engine. It is preferred that the diesel engine is a conventional (i.e., traditional) diesel engine.

It is preferred that the lean burn engine be configured or adapted for operation with a fuel, preferably diesel fuel, comprising ≤50ppm sulfur, more preferably ≤15ppm sulfur, such as ≤10ppm sulfur, and even more preferably ≤5ppm sulfur ,

The vehicle may be a light duty diesel vehicle (LDV), for example, as defined in US legislation or European legislation. A light-duty diesel vehicle typically has a weight of <2840 kg, more preferably a weight of <2610 kg.

In the US, a light-duty diesel vehicle (LDV) designates a diesel vehicle with a gross weight of ≤ 8500 pounds (US Ibs). In Europe, the term Light Load Diesel Vehicle (LDV) refers to: (i) passenger vehicles with no more than eight seats in addition to the driver's seat and with a maximum mass of not more than 5 tonnes, and (ii) vehicles carrying goods with a maximum mass of not more than 12 tons.

Alternatively, the vehicle may be a heavy duty diesel vehicle (HDV), such as a diesel vehicle with a gross weight of> 8500 pounds (US Ibs), as defined in US legislation.

Another aspect of the invention is a method of treating an exhaust gas from an internal combustion engine, the method comprising contacting the exhaust gas with the NO _x absorber catalyst as described above or any one of the above-described first through fifth exhaust systems. In preferred processes, the exhaust gas is a rich gas mixture. In further preferred methods, the exhaust gas cycles between a rich gas mixture and a lean gas mixture.

In some preferred methods of treating an exhaust gas from an internal combustion engine, the exhaust gas is at a temperature of about 150 ° C to 300 ° C.

In other preferred methods of treating an exhaust gas from an internal combustion engine, the exhaust gas is combined with one or more other emission control devices in addition to that herein previously described NO _x absorber catalyst, brought into contact. The emission control device or devices are preferably downstream of the NO _x absorber catalyst.

Examples of another emission control device comprising a diesel particulate filter (DPF), a lean NO _x trap (LNT), a lean _NOx catalyst (LNC), a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF ™) catalyst, an ammonia slip catalyst (ASC), a cold start catalyst (dCSC ™), and combinations of two or more thereof. Such emission control devices are all well known in the art.

Some of the aforementioned emission control devices have filter substrates. An emission control device having a filter substrate may be selected from the group consisting of a diesel particulate filter (DPF), a catalyzed soot filter (CSF) and a selective catalytic reduction filter (SCRF ™) catalyst.

It is preferred that the method comprises in contacting the exhaust gas with an emission control device of the _X-trap from a lean NO (LNT), an ammonia-slip catalyst (ASC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR) catalyst, a catalyzed soot filter (CSF), a selective catalytic reduction filter (SCRF ™) catalyst and combinations of two or more thereof existing group is selected. More preferably, the emissions control device is selected from the group consisting of a diesel particulate filter (DPF), a selective catalytic reduction (SCR) catalyst, a catalyzed particulate filter (CSF), a selective catalytic reduction filter (SCRF ™) catalyst, and combinations of two or more here. More preferably, the emission control device is a Selective Catalytic Reduction (SCR) catalyst or a Selective Catalytic Reduction Filter (SCRF ™) catalyst.

When the method of the invention comprises contacting the exhaust gas with an SCR catalyst or SCRF ™ catalyst, the method may further include injecting a nitrogen-containing reducing agent, such as ammonia, or an ammonia precursor, such as urea or ammonium formate , preferably urea, into the exhaust gas downstream of the lean NO _x trap catalyst and upstream of the SCR catalyst or the SCRF ™ catalyst.

Such an injection may be performed by an injector. The injector may be fluidly connected to a source (e.g., a tank) of a precursor of a nitrogenous reductant. Valve-controlled metering of the precursor into the exhaust may be controlled by suitably programmed engine management means and closed loop or open loop feedback provided by sensors monitoring the composition of the exhaust gas.

Ammonia may also be generated by heating ammonium carbamate (a solid) and the generated ammonia may be injected into the exhaust gas.

Alternatively, or in addition to the injector, ammonia may be generated in situ (e.g., during a rich regeneration of an LNT located upstream of the SCR catalyst or SCRF ™ catalyst). Thus, the method may further comprise enriching the exhaust gas with hydrocarbons.

The SCR catalyst or SCRF ™ catalyst may comprise a metal selected from the group consisting of at least one of Cu, Hf, La, Au, In, V, lanthanides, and Group VIII transition metals (eg, Fe) wherein the metal is supported on a refractory oxide or molecular sieve. The metal is preferably selected from Ce, Fe, Cu and combinations of any two or more thereof, more preferably the metal is Fe or Cu.

The refractory oxide for the SCR catalyst or the SCRF ™ catalyst may be selected from the group consisting of Al ₂ O ₃ , TiO ₂ , CeO ₂ , SiO ₂ , ZrO ₂ and mixed oxides containing two or more thereof , The non-zeolite catalyst may further comprise tungsten oxide (eg, V ₂ O ₅ / WO ₃ / TiO ₂ , WO _X / CeZrO ₂ , WO _X / ZrO ₂ or Fe / WO _X / ZrO ₂ ).

It is particularly preferred if an SCR catalyst, a SCRF ™ catalyst or a washcoat thereof comprises at least one molecular sieve such as an aluminosilicate zeolite or a SAPO. The at least one molecular sieve may be a small pore, a medium pore or a large pore molecular sieve. By "small pore molecular sieve" we mean herein molecular sieves containing a maximum ring size of 8, such as CHA; By "medium pore molecular sieve" herein we mean a molecular sieve containing a maximum ring size of 10, such as ZSM-5; and by "large pore molecular sieve" we mean herein a molecular sieve having a maximum ring size of 12, such as beta. Small pore molecular sieves are potentially advantageous for use in SCR catalysts.

In the method of treating an exhaust gas of the present invention, preferred molecular sieves for an SCR catalyst or SCRF ™ catalyst are synthetic aluminosilicate zeolite molecular sieves selected from the group consisting of AEI, ZSM-5, ZSM-20, ERI including ZSM. 34, mordenite, ferrierite, BEA including beta, Y, CHA, LEV including Nu-3, MCM-22 and EU-1, preferably AEI or CHA, and having a silica to alumina ratio of about 10 to about 50, such as from about 15 to about 40.

EXAMPLES

The invention will now be illustrated by the following non-limiting examples.

materials

All materials are commercially available and were obtained from known suppliers unless otherwise stated.

example 1

A slurry was prepared by milling alumina to a d ₉₀ <20 microns. Alumina binder was added and the slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This coating comprised 1.0 g inch ^-3 alumina and 0.1 g inch ^-3 alumina binder.

Example 2

A slurry was prepared by milling alumina to a d ₉₀ <20 microns. A suspension of colloidal silica was added, followed by alumina binder, and the mixture was stirred to homogenize. This slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This coating comprised 0.5 g inch ^-3 alumina, 0.5 g inch ^-3 silica, and 0.1 g inch ^-3 alumina binder.

Example 3

1. (a) Pd nitrate was added to a slurry of a small pore zeolite with AEI structure and the whole was stirred. Alumina binder was added and then the slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating comprising a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 30 g ft ^-3 .
2. (b) A second slurry was prepared using a silica-alumina powder ground to a d ₉₀ <20 micrometer. Soluble platinum salt followed by beta zeolite was added so that the slurry comprised 74 mass% silica-alumina and 26 mass% zeolite. A bismuth nitrate solution was added and the slurry was stirred to homogenize. The resulting washcoat was applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 30 g ft ^-3 . The bi-loading was 50 g ft ^-3 .
3. (c) A third slurry was prepared using a Mn-doped silica-alumina powder milled to a d ₉₀ <20 microns. Soluble platinum salt was was added and the mixture was stirred to homogenize. The slurry was applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 30 g ft ^-3 .

Example 4

A first slurry was prepared as in Example 3 (a) and applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating comprising a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 30 g ft ^-3 .

A second slurry was prepared by milling alumina to a d ₉₀ <20 microns. This slurry was applied to the flow through monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This coating comprised 1.0 g inch ^-3 alumina.

A third slurry was prepared using a silica-alumina powder ground to a d ₉₀ <20 micrometer. Soluble platinum salt followed by beta zeolite was added so that the slurry comprised 74 mass% silica-alumina and 26 mass% zeolite. A bismuth nitrate solution was added and the slurry was stirred to homogenize. The resulting washcoat was applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 30 g ft ^-3 . The bi-loading was 50 g ft ^-3 .

A fourth slurry was prepared using a Mn-doped silica-alumina powder milled to a d ₉₀ <20 microns. Soluble platinum salt was added and the mixture was stirred to homogenize. The slurry was applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 30 g ft ^-3 .

Example 5

A first slurry was prepared as in Example 3 (a) and applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating comprising a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 30 g ft ^-3 .

A second slurry was prepared using ceria with a particle size d ₉₀ <20 microns. Alumina binder was added and the mixture was stirred to homogenize. The coating was applied to the flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This inorganic oxide coating included 1.0 g inch ^-3 ceria and 0.2 g inch ^-3 alumina binder.

A third slurry was prepared as in Example 3 (b) and applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 30 g ft ^-3 . The bi-loading was 50 g ft ^-3 .

A fourth slurry was prepared as in Example 3 (c) and applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 30 g ft ^-3 .

Example 6

A first slurry was prepared as in Example 3 (a) and applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The Coating was dried and calcined at 500 ° C. A coating comprising a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 30 g ft ^-3 .

A second slurry was prepared using ceria with a particle size d ₉₀ <20 microns. Alumina binder was added, followed by soluble Pt salt. The slurry was stirred to homogenize and then applied to the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. This coating comprised of an inorganic oxide 1.0 g inch ^-3 ceria, 0.2 g of alumina ^-3 inch and a Pt loading of 10 g ft ^-3.

A third slurry was prepared as in Example 3 (b) and applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 30 g ft ^-3 . The bi-loading was 50 g ft ^-3 .

A fourth slurry was prepared as in Example 3 (c) and applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 30 g ft ^-3 .

Experimental results

The catalysts of Examples 1 to 6 were hydrothermally aged at 750 ° C for 15 hours with 10% water. The catalysts were mounted on a light load diesel engine mounted on a bench in a position closely coupled to the turbocharger. The emissions were measured before and after the catalyst. Catalyst Examples 1 and 2 were tested via a simulated Worldwide Harmonized Light Duty Test Cycle (WLTC). The NO ₂ reduction performance of Examples 1 and 2 is determined by the difference between the cumulative NO ₂ emission before the catalyst compared to the cumulative NO ₂ emission after the catalyst over a complete WLTC test. Catalyst Examples 3 to 6 were tested for performance via a New Emission Cycle Test (NEDC). The NO _x adsorption performance of Examples 3 to 6 is determined by the difference between the cumulative NO _x emission before the catalyst compared to the cumulative NO _x emission after the catalyst at 1000 seconds in the NEDC test. The difference between the cumulative NO _x emissions before and after the catalyst is attributed to the NO _x adsorbed by the catalyst.

Table 1 shows the performance for NO ₂ reduction of Catalyst Examples 1 and 2 via the WLTC test. Table 1 Example no. cumulative NO ₂ before the catalyst (g) cumulative NO ₂ after the catalyst (g) cumulative NO ₂ reduction (%) 1 1.0 0.68 32 2 1.0 0.33 67

The results in Table 1 show that the cumulative NO ₂ emissions after the catalyst are less than the cumulative NO ₂ emissions before the catalyst in Catalyst Examples 1 and 2. Table 1 also shows the percentage reduction in cumulative NO ₂ after the exhaust gas has passed through the catalysts. Examples 1 and 2 comprise an inorganic oxide carrier according to the invention (ie, a nitrogen dioxide reducing material), showing that the inorganic oxide is effective for NO ₂ reduction.

Table 2 shows the performance for NO _X adsorption of Catalyst Examples 3 to 6 at 1000 seconds in the NEDC test. Table 2 Example no. NO _X , adsorbed at 1000 seconds (g) 3 0.49 4 0.57 5 0.70 6 0.74

The results in Table 2 show that Examples 4, 5 and 6 adsorb and retain a larger amount of NO _x than Example 3 at 1000 seconds in the NEDC test. Examples 4, 5 and 6 comprise a layer of inorganic oxide prepared according to the invention. Example 3 does not include a layer comprising a layer of inorganic oxide of the invention (ie, a nitrogen dioxide reducing material). Example 6 involves a low loading of Pt with the inorganic oxide. The low loading of Pt is not effective in oxidizing NO to NO ₂ and improved NO _X adsorption is achieved compared to Example 3.

Example 7

Pd nitrate was added to a slurry of a small pore zeolite with AEI structure and stirred. Alumina binder was added and then the slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating containing a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 80 g.ft ³ .

A second slurry was prepared using a silica-alumina powder ground to a d ₉₀ <20 micrometer. Soluble platinum salt followed by beta zeolite was added so that the slurry comprised 74 mass% silica-alumina and 26 mass% zeolite. A bismuth nitrate solution was added and the slurry was stirred to homogenize. The resulting washcoat was applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 68 g ft ^-3 . The bi-loading was 50 g ff ^-3 .

A third slurry was prepared using a Mn-doped silica-alumina powder milled to a d ₉₀ <20 microns. Soluble platinum salt was added and the mixture was stirred to homogenize. The slurry was applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 68 g ft ^-3 .

Example 8

Pd nitrate was added to a slurry of a small pore zeolite with AEI structure and stirred. Alumina binder was added and then the slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating containing a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 80 g.ft ³ .

A second slurry was prepared by milling alumina to a d ₉₀ <20 microns. A suspension of colloidal silica was added and the mixture was stirred to homogenize. This slurry was applied to the flow through monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This coating comprised 0.5 g inch ^-3 alumina and 0.5 g inch ^-3 silica.

A third slurry was prepared using a silica-alumina powder ground to a d ₉₀ <20 micrometer. Soluble platinum salt followed by beta zeolite was added so that the slurry comprised 74 mass% silica-alumina and 26 mass% zeolite. A bismuth nitrate solution was added and the slurry was stirred to homogenize. The resulting washcoat was exposed to the channels at the inlet end of the flow through monolith Use of established coating techniques applied. The part was then dried. The Pt loading of this coating was 68 g ft ^-3 . The bi-loading was 50 g ft ^-3 .

A fourth slurry was prepared using a Mn-doped silica-alumina powder milled to a d ₉₀ <20 microns. Soluble platinum salt was added and the mixture was stirred to homogenize. The slurry was applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 68 g ft ^-3 .

Example 9

Pd nitrate was added to a slurry of a small pore zeolite with AEI structure and stirred. Alumina binder was added and then the slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating containing a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 80 g.ft ³ .

A second slurry was prepared by milling alumina to a d ₉₀ <20 microns. A suspension of colloidal silica was added and the mixture was stirred to homogenize. This slurry was applied to the flow through monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This coating comprised 1.0 g inch ^-3 alumina and 0.5 g inch ^-3 silica.

A third slurry was prepared using a silica-alumina powder ground to a d ₉₀ <20 micrometer. Soluble platinum salt followed by beta zeolite was added so that the slurry comprised 74 mass% silica-alumina and 26 mass% zeolite. A bismuth nitrate solution was added and the slurry was stirred to homogenize. The resulting washcoat was applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 68 g ft ^-3 . The bi-loading was 50 g ft ^-3 .

A fourth slurry was prepared using a Mn-doped silica-alumina powder milled to a d ₉₀ <20 microns. Soluble platinum salt was added and the mixture was stirred to homogenize. The slurry was applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 68 g ft ^-3 .

Example 10

Pd nitrate was added to a slurry of a small pore zeolite with AEI structure and stirred. Alumina binder was added and then the slurry was applied to a 400 cell per square inch cordierite flow monolith using established coating techniques. The coating was dried and calcined at 500 ° C. A coating containing a Pd-exchanged zeolite was obtained. The Pd loading of this coating was 80 g.ft ³ .

A second slurry was prepared by milling alumina to a d ₉₀ <20 microns. A suspension of colloidal silica was added and the mixture was stirred to homogenize. This slurry was applied to the flow through monolith using established coating techniques. The coating was dried and calcined at 500 ° C. This coating comprised 1.0 g inch ^-3 silica and 0.5 g inch ^-3 alumina.

A third slurry was prepared using a silica-alumina powder ground to a d ₉₀ <20 micrometer. Soluble platinum salt followed by beta zeolite was added so that the slurry comprised 74 mass% silica-alumina and 26 mass% zeolite. A bismuth nitrate solution was added and the slurry was stirred to homogenize. The resulting washcoat was applied to the channels at the inlet end of the flow through monolith using established coating techniques. The part was then dried. The Pt loading of this coating was 68 g ft ^-3 . The bi-loading was 50 g ft ^-3 .

A fourth slurry was prepared using a Mn-doped silica-alumina powder milled to a d ₉₀ <20 microns. Soluble platinum salt was added and the mixture was stirred to homogenize. The slurry was applied to the channels at the outlet end of the flow through monolith using established coating techniques. The coating was then dried and calcined at 500 ° C. The Pt loading of this coating was 68 g ft ^-3 .

Experimental results

The catalysts of Examples 7, 8, 9 and 10 were hydrothermally aged at 750 ° C for 15 hours with 10% water. They were tested for performance through a Worldwide Harmonized Light Duty Test Cycle (WLTC). The catalyst was mounted in a position closely coupled to the turbocharger on a 2.0 liter diesel engine mounted on a bench. The emissions were measured before and after the catalyst. The NO _x adsorption performance of each catalyst was determined as the difference between the cumulative NO _x emission before the catalyst compared to the cumulative NO _x emission downstream of the catalyst. The difference between the cumulative NO _x emissions before and after the catalyst is attributed to the NO _x adsorbed by the catalyst. The CO and HC oxidation performance is calculated as the cumulative conversion efficiency over the entire test cycle at 1000 seconds.

Table 3 shows the NO _x absorption performance of Catalyst Examples 7, 8, 9 and 10 at 1000 seconds in the WLTC test. Table 3 Example no. NO _X , adsorbed at 1000 seconds (g) 7 0.62 8th 0.75 9 0.75 10 0.75

The results in Table 3 show that Examples 8, 9 and 10 adsorb a greater amount of NO _x than Example 7. Examples 8, 9 and 10 comprise a silica and alumina layer used to reduce nitrogen dioxide according to the invention suitable is.

Table 4 shows the conversion efficiency for CO and HC oxidation of Catalyst Examples 1, 2, 3 and 4 at 1000 seconds in the WLTC test. Table 4 Example no. CO conversion (%) HC conversion (%) 7 67 81 8th 81 85 9 82 86 10 79 85

The results in Table 4 show that Examples 8, 9 and 10 convert higher percentages of CO than Example 7. Examples 8, 9 and 10 include a silica and alumina layer suitable for reducing nitrogen dioxide and this is advantageous for CO oxidation. All Examples 7, 8, 9 and 10 convert a similar percentage of HC.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2012/166868 [0035]
• WO 9947260 [0128]
• WO 2007/077462 [0128]
• WO 2011/080525 [0128]
• US 4300956 [0139]
• US 5146743 [0139]
• US 6513324 [0139]

Claims (19)

A NO _X absorber catalyst for treating an exhaust gas from a diesel engine, comprising: a first region comprising a NO _x absorber material comprising a molecular sieve catalyst, the molecular sieve catalyst comprising a noble metal and a first molecular sieve, and wherein the first molecular sieve contains the noble metal; a second region comprising a nitrogen dioxide reducing material comprising at least one inorganic oxide; and a substrate having an inlet end and an outlet end; wherein the second region is substantially free of platinum group metals. NO _X absorber catalyst according to Claim 1 wherein the noble metal comprises palladium. NO _X absorber catalyst according to Claim 1 or Claim 2 wherein the molecular sieve comprises an aluminosilicate skeleton, an aluminophosphate skeleton or a silicoaluminophosphate skeleton. The NO _x absorber catalyst of any one of the preceding claims, wherein the molecular sieve is selected from a small pore molecular sieve, a medium pore molecular sieve, and a large pore molecular sieve. A NO _X absorber catalyst according to any one of the preceding claims, wherein the molecular sieve is a small pore molecular sieve having a framework type selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, STI, THO, TSC, UEI, UFI, VNI, YUG, ZON and a mixture or intergrowths of any two or more thereof. NO _X absorber catalyst according to Claim 4 wherein the small pore molecular sieve has a framework type which is AEI, CHA or STI. A NO _x absorber catalyst according to any one of the preceding claims wherein the molecular sieve has an aluminosilicate backbone and a silica to alumina molar ratio of 10 to 200. NO _x absorber catalyst according to any one of the preceding claims, wherein said at least one inorganic oxide is selected from the group consisting of alumina, ceria, magnesia, silica, titania, zirconia, niobium oxide, tantalum oxides, molybdenum oxides, tungsten oxides and mixed oxides or composite oxides thereof. NO _x adsorber catalyst according to any one of the preceding claims, wherein said at least one inorganic oxide is selected from the group consisting of alumina, silica and mixed oxides or composite oxides thereof. The NO _x adsorber catalyst of any of the preceding claims, wherein the at least one inorganic oxide is not catalytically active in the selective catalytic reduction (SCR) of NO _x with a nitrogen-containing reductant. NO _x absorber catalyst according to any one of the preceding claims, wherein the second region comprises a molecular sieve. The NO _X absorber catalyst according to any one of the preceding claims, wherein said at least one inorganic oxide comprises an inorganic oxide doped with a dopant, said dopant being an element selected from the group consisting of tungsten (W), silicon (Si) , Titanium (Ti), lanthanum (La), praseodymium (Pr), hafnium (Hf), yttrium (Y), ytterbium (Yb), samarium (Sm), neodymium (Nd) and a combination of two or more thereof or one Oxide consists of this. The NO _x absorber catalyst of any one of the preceding claims, further comprising a diesel oxidation catalyst (DOC) region. NO _X absorber catalyst according to any one of the preceding claims, wherein the substrate is a flow-through monolith or a filter monolith. An exhaust system comprising a NO _x absorber catalyst as defined in any of Claims 1 to 14 and an emission control device. Exhaust system after Claim 15 Wherein the emission control device is selected from the group consisting of emission control devices are selected from the group consisting of a diesel particulate filter (DPF), a lean NO _x trap (LNT), a lean _NOx catalyst (LNC ), a passive NO _x adsorber (PNA), a cold start catalyst (dCSC), a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF ™ ) Catalyst, an ammonia slip catalyst (ASC) and combinations of two or more thereof. A vehicle comprising a lean burn engine and a NO _x absorber catalyst as defined in any of Claims 1 to 14 or an exhaust system as defined in Claim 15 or Claim 16 includes. Vehicle according to Claim 17 wherein the lean burn engine is configured for operation with diesel fuel comprising ≤ 50 ppm sulfur. A method of treating an exhaust gas from a lean burn engine, which comprises contacting the exhaust with a NO _x absorber catalyst according to any one of Claims 1 to 14 or guiding the exhaust gas through an exhaust system according to Claim 15 or Claim 16 includes.

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